In a conventional radiography system, an x-ray source is caused to direct a divergent area beam of x-rays through a patient. A cassette containing an x-ray sensitive phosphor screen and film, sensitive to light and x-rays, is positioned in the x-ray path on the side of a patient opposite the source. Radiation passing through the patient's body is attenuated in varying degrees in accordance with the various types of tissue through which the x-rays pass. The attenuated x-rays from the patient emerge in a pattern, and strike the phosphor screen, which in turn exposes the film. The x-ray film is processed to yield a visible image which can be interpreted by a radiologist as defining internal body structure and/or condition of the patient.
Many operating mode geometries are used in radiography and fluoroscopy.
In some applications, the patient reclines on an x-ray table having a top surface through which x-rays can pass with little attenuation. The source is located above the table and projects x-rays downwardly through the patient's body. The table is equipped with means, often called a "bucky", for accommodating and holding in place a radiographic film cassette just below the surface of the table.
In other applications, the source is located beneath the table top and projects x-rays upwardly through the table top and through the patient's body. A filmer assembly, having means to accommodate and support a radiographic film cassette, is located above the patient's body and aligned in the beam. These two applications are often referred to generally as "horizontal" radiography.
In another application, known as vertical radiography, the patient stands upright and a source is positioned in front of his body to propagate radiation through it along a geneally horizontal path. The radiographic film cassette or a spot filmer is supported behind the patient and is exposed by the x-rays.
In another type of radiography, known as "lateral", the patient reclines on the table, and the source is positioned generally beside the table to propagate its x-ray beam transverse to the longitudinal dimension of the table and through the patient's body. The radiographic cassette is appropriately supported on the opposite side of the table to receive the x-rays passing through the patient's body.
Still other radiogrpahic techniques are known as "oblique" work, in which the source is tilted or angled about one or more axes with respect to the table top to propagate x-rays through a patient lying upon the table. In one so-called oblique mode, the x-ray source is suspended over the table, and is rotated to an oblique angle, with respect to the table top, about an axis which is substantially horizontal and is perpendicular to the longitudinal dimension of the table.
Another radiographic technique defined here as "off table work" is typically performed using ceiling mounted x-ray systems or floor to ceiling mounted systems.
In fluoroscopy, a real time substantially continuous image, rather than a snapshot, of the patient's internal body structure is produced. The source directs x-rays through the patient's body, which are received by a fluoro device located on the opposite side of the patient. The fluoro device includes known means for producing a continuous image of the emergent pattern of x-rays transmitted by the patient's body. In fluoroscopy, the x-ray source is operated at a lower output level than in radiography. The output in fluoroscopy, however, rather than being a single pulse, is continuous.
Known types of fluoro devices employ a scintillation screen which responds to the incident pattern of x-rays to produce a directly visible image. Other types of fluoroscopic devices employ an image intensifier tube, which receives the x-ray pattern at a relatively large input face, and produces at an output face a corresponding image whose brightness is substantially enhanced with respect to the brightness of a simple scintillation screen. Where an image tube is used, the output is often viewed by a television camera and displayed on a monitor.
In fluoroscopy, mode geometries include those discussed above in connection with radiography, except for lateral, oblique and off-table work.
It can be seen from the foregoing discussion that, in order to accomplish all the various modes of radiography and fluoroscopy, the source and detector, be it radiographic film, a filmer assembly, or a fluoro device, must be positionable in a large multiplicity of locations with respect to the x-ray table and to the patient's body. This situation is complicated where a system is needed having the capability of practicing imaging in both radiographic and fluoroscopic modes, because of the necessity to support and position not only the radiation source, but also a radiographic film cassette, a filmer assembly, a fluoro device, and the patient.
Prior art x-ray systems either do not have the capability and versatility for performing operations in all the modes discussed above, or they are quite complex, bulky, and heavy, and require a permanent or fixed installation, such as including supporting walls and ceilings. Such systems also require large floor area to achieve such versatility.
One type of prior art system employs an x-ray source mounted only for location under the x-ray table in conjunction with a fluoro device and a filmer mounted on the table. Such devices obviously suffer from the disadvantage that they cannot be adapted to operate to position the source both above and below the table.
Other systems attempt to deal with the disadvantages of such systems by employing two sources, a first located above the table, a second located beneath it. The first source, located above the table, is typically mounted on either a ceiling supported track, a wall mounted track, or other tower structure. In such instances, the second source, located below the table, is dedicated for undertable use exclusively, and the above-table source is dedicated for overtable work. Such systems cannot stand independently of the support means provided by a fixed wall or ceiling.
Most prior art systems provide at least some of the desired component movement by means of electromechanical servo systems driven by controllable electric motors. The requirement for these servo drives is a disadvantage where space, weight and reliability are considerations, or where electric power is not readily available.
While systems such as those described above have been found satisfactory for operation in permanent installations, such as in permanent doctors' offices and large hospitals, these systems are inordinately complex and bulky for convenient use in portable applications. Such portable applications can include portable x-ray equipment for transport to a scene of traumatic injury, such as for use in conjunction with domestic trauma treatment centers, and in transportable military hospitals and first aid stations.
In such applications, it is particularly desireable that all equipment be as simple and reliable as possible, since repair capability may be inaccessible in the field. The equipment should be able to withstand repeated assembly and knockdown for transport. It must be capable of being knocked down, preferably without tools, into relatively small components which can be carried by humans without the aid of mechanical lifting and transport equipment, such as where it would be desireable to load an x-ray system in pieces into a vehicle for quick transport to and reassembly at a site of need.
Needless to say, x-ray equipment designed for portable application must be sufficiently rugged to resist damage or maladjustment resulting from vibration and other shock which normally occurs during transport of field equipment.
Another problem inherent in portable x-ray equipment is that, often, the equipment is used where electric power is in limited supply and form. It is sometimes a problem to find sufficient electric power, or the needed frequency, phase and/or voltage, to actuate relatively heavy electromechanical components such as motors and other servo equipment used to drive prior art type radiographic equipment.
The requirements of radiographic equipment used for initial evaluation of extensive traumatic injury often differ somewhat from the requirements for radiographic equipment used in permanent installations. Often, in portable units such as military field hospitals, sometimes called "MASH", the most important requirement for a radiographic system is to be able to reliably scan large areas of the human body very quickly, convert rapidly from one operating mode to another, and to rapidly produce images of reasonable quality illustrating gross traumatic injury caused by shrapnel, bullets and the like. It is also important to be able to perform a variety of radiographic and fluoroscopic procedures with little or no patient movement.
One previous military system was constructed in modular manner to break down into subassemblies which could be individually loaded into reusable containers for transport. This system, dating back to pre-World War II, was known as the "50/90" system, manufactured by Picker Corporation, of Cleveland, Ohio, USA. Though the 50/90 system was satisfactory for some uses, it had several disadvantages. It had very limited provision for multiangle oblique radiographic operation. It had no spot filmer capability. Its fluoro was done with only a phosphor screen. In vertical radiography, the bucky could not be employed.
It is an object of this invention to provide a lightweight, rugged, compact, versatile, reliable, simple, easily disassembled radiographic/fluoroscopic system capable of executing a large variety of radiographic and fluoroscopic operational modes, and without the need for the application of electromechanical power to move system components.